In Climate: Up the Down Escalator

January 2, 2018

WASHINGTON (AP) — Anchorage, Alaska, was warmer Tuesday than Jacksonville, Florida. The weather in the U.S. is that upside down.

That’s because the Arctic’s deeply frigid weather escaped its regular atmospheric jail that traps the worst cold. It then meandered south to the central and eastern United States.

And this has been happening more often in recent times, scientists say.

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WHY IS IT SO COLD?

Super cold air is normally locked up in the Arctic in the polar vortex , which is a gigantic circular weather pattern around the North Pole. A strong polar vortex keeps that cold air hemmed in.

“Then when it weakens, it causes like a dam to burst,” and the cold air heads south, said Judah Cohen, a winter storm expert for Atmospheric Environmental Research, a private firm outside Boston.

“This is not record-breaking for Canada or Alaska or northern Siberia, it’s just misplaced,” said Cohen, who had forecast a colder than normal winter for much of the U.S.

IS THIS UNUSUAL?

Yes, but more for how long — about 10 days — the cold has lasted, than how cold it has been. On Tuesday, Boston tied its seven-day record for the most consecutive days at or below 20 degrees that was set exactly 100 years ago.

More than 1,600 daily records for cold were tied or broken in the last week of December, according to the National Oceanic and Atmospheric Administration. For Greg Carbin of the National Weather Service’s Weather Prediction Center, the most meaningful statistics are how last week’s average temperature was the second coldest in more than a century of record-keeping for Minneapolis, Chicago, Detroit and Kansas City, third coldest in Pittsburgh and fifth coldest in New York City.

The situation is similar to what we experienced in the “Polar Vortex” winters of 2013-14.

AP continued:

IS IT JUST THE U.S.?

Pretty much. While the United States has been in the deep freeze, the rest of the globe has been toastier than normal. The globe as a whole was 0.9 degrees (0.5 degrees Celsius) warmer than normal Tuesday and the Arctic was more than 6 degrees warmer than normal (3.4 degrees Celsius), according to the University of Maine Climate Change Institute’s analysis .

WHAT’S NEXT?

The cold will continue and could actually worsen for much of the East Coast this weekend because of a monster storm that’s brewing in the Atlantic and Caribbean, what meteorologists are calling a “snow hurricane” or “bomb cyclone.”

But forecasters don’t think the storm will hit the East Coast, keeping most of the snow and worst winds over open ocean, although parts of the Northeast are still likely to get high winds, waves and some snow.

“For the Northeast, this weekend might be the coldest of the coldest with the storm,” said Jason Furtado, a University of Oklahoma meteorology professor. “We could be ending (the cold snap) with a big hurrah.”

This past July was the hottest single month in Earth’s recorded history, but warming isn’t the only danger climate change holds in store. Recent years have seen a dramatic increase in the simultaneous occurrence of extremely cold winter days in the Eastern United States and extremely warm winter days in the West, according to a Stanford-led study published in Journal of Geophysical Research Atmospheres. Human-caused emissions of greenhouse gases are likely driving this trend, the researchers report.

“There’s this idea that the past few winters were more extreme than usual, particularly since the conditions in the East and West were so different,” said senior author Noah Diffenbaugh, an associate professor of Earth system science at the School of Earth, Energy & Environmental Sciencesand a senior fellow at the Stanford Woods Institute for the Environment. “Looking back at temperature data from the past 35 years, we’ve found that in fact 2013-2014 and 2014-2015 did have the biggest difference in winter temperature between the East and West.”

Understanding the physical factors driving extreme weather could provide policymakers with more reliable information with which to prepare for short-term weather disasters such as blizzards and cold snaps. Long-term planning and development would benefit too. For instance, understanding the likelihood of droughts could help engineers better plan the development and management of infrastructure to provide reliable water supplies.

In the past three years alone, the combination of heat-related drought in the West and Arctic conditions in the East have pinched the national economy, costing several billion dollars in insured losses, government aid and lost productivity (read more). When such weather extremes occur at the same time, they threaten to stretch emergency responders’ disaster assistance abilities, strain resources such as interregional transportation and burden taxpayer-funded disaster relief.

‘Warm West, cold East’ trends related

The Stanford study finds that the occurrence and severity of “warm West, cold East” winter events increased significantly between 1980 and 2015. This is partly because the winter temperature has warmed more in the West than in the East, increasing the odds that warm days in the West coincide with cold days in the East. Along with warming of the West, a “ridge-trough” pattern of high atmospheric pressure in the West and low atmospheric pressure in the East has also been producing greater numbers of winter days on which large areas of the West and East experience extreme temperatures at the same time.